Connecting ball joint, for example for an anti-roll bar of a running vehicle

ABSTRACT

The invention relates to a connecting ball joint ( 10 ), for example an anti-roll bar of a running vehicle, said ball joint ( 10 ) comprising a straight support ( 20 ) running along a general axis of elongation (xx′) and an elastically deformable member ( 30 ) mounted around this support ( 20 ). This ball joint has the characteristic that its elastically deformable member ( 30 ) comprises at least one laminated structure ( 35; 135 ) made up of (a) layer(s) ( 32 ) of elastically deformable flexible material and of (a) layer(s) ( 34 ) of more rigid material.

[0001] The invention relates to a connecting ball joint particularly foran anti-roll bar of a running vehicle, and especially for a bogie and/orbody of a high speed train.

[0002] In the particular, but nonlimiting, field of anti-roll bars (alsoknown as stabilizing bars or anti-sway bars) commonly used in automotiveor rail suspension systems, the function of such a bar is to oppose thevertical forces transmitted to the wheels in bends when the inertia ofthe vehicle causes the latter to roll transversely.

[0003] The means of connecting or of fixing an anti-roll bar to thechassis of the vehicle or to the suspension arms may be varied and, inparticular, may comprise bearings or ball joints provided, for example,with an elastic bushing. Such bearings or ball joints have variousfunctions, aside that of fixing the bar to the chassis, such as thefunction of filtering the forces, during roll, between the structure ofthe vehicle and said bar, of the function of filtering low-amplitudevibration.

[0004] Various types of ball joint exist which allow a certainrotational deflection between two rigid parts. For example, the balljoint may be fitted with a fairly thick rubber or polycarbonate bushingwith a frictional connection. It is also possible to anticipate the useof lubricated ball joints.

[0005] However, such ball joints are not yet satisfactory because theydo not correctly filter vibration, and this leads to unpleasant noisedue, for example, to the excessive stiffness of the parts which prevent,or following degradation of the parts which causes play and rattle. Theyare also not very strong. Finally, they do not have good ratios betweenangular excursion and stiffness (radial, rotational and conicaltorsional stiffnesses).

[0006] The object of the invention is therefore to solve at least someof these problems.

[0007] To do that, the invention relates to a connecting ball joint, forexample an anti-roll bar of a running vehicle, said ball jointcomprising a straight support running along a general axis of elongationand an elastically deformable member mounted around this support,characterized in that the elastically deformable member comprises atleast one laminated structure made up of (a) layer(s) of elasticallydeformable flexible material and of (a) layer(s) of more rigid material.

[0008] In general, the elastically deformable member will comprise meansfor preloading its laminated structure, particularly for preventing theelastically deformable layer from working in tension.

[0009] According to one embodiment, the elastically deformable membermay comprise two coaxial annular laminated structures and two annularsleeve tubes each mounted around one laminated structure to preloadtheir elastically deformable layers once these sleeve tubes have beenconnected together using fixing means, the ball joint then having aplane of section roughly perpendicular to the axis of the support.

[0010] In particular, the two sleeve tubes will each have a contactsurface perpendicular to the axis of the support and will be weldedperipherally at these surfaces.

[0011] According to another embodiment, the elastically deformablemember may have a plane of section passing through the axis of thesupport and may comprise two approximately hemispherical laminatedstructures extending along the axis xx′ and two half sleeve tubes, alsoapproximately hemispherical, each surrounding a laminated structure topreload their elastically deformable layers.

[0012] In particular, an outer tube may be crimped around the halfsleeve tubes.

[0013] In order to allow good angular excursion of the ball joint, whileat the same time avoiding have to resort to a lubricant, each laminatedstructure will consist of an alternation of approximately hemisphericallayers of elastically deformable (hyperelastic) flexible material and ofapproximately hemispherical layers (or cups) of a more rigid material.The good shear properties of rubber are therefore put to full use inorder to improve this ability to rotate. Indeed this material has arelatively low shear modulus (of the order of 0.5 to 2 MPa) for a highcompression modulus (of the order of 1100 MPa).

[0014] Advantageously, each laminated structure will have a hyperelasticflexible layer at each of its ends, one in contact with a sphericalcore, and the other in contact with the preloading means.

[0015] By way of example, the hyperelastic flexible material may be anatural rubber and the rigid material may be a metal, and the layers offlexible material and the layers of rigid material may each have athickness of the order of 1 mm.

[0016] In general, the ball joint also has a radial stiffness higherthan the ball joints of the prior art, for equivalent bulk andequivalent possible excursion, and in particular have a radial stiffnesswhich is higher than its torsional and/or torsional conical stiffness.

[0017] In addition, the elastically deformable flexible layers areconnected to the more rigid layers in such a way that these flexiblelayers, when subjected to rotational forces about the axis of thesupport or forces of conical rotation about any axis perpendicular tothe axis of the support, experience mainly shear forces, with noslipping with respect to the more rigid layers. Of course, thesehyperelastic layers are subjected to radial compressive (and tensile)stresses.

[0018] The invention also relates to an anti-roll bar for a runningvehicle such as a high speed train, equipped with a connecting balljoint as described hereinabove.

[0019] Other features, details and advantages of the invention willbecome apparent on reading the description which follows, given by wayof example with reference to the appended drawings, in which:

[0020]FIG. 1 is a front view of the ball joint according to theinvention,

[0021]FIG. 2 is a side view of FIG. 1,

[0022]FIG. 3 is a sectional view of FIG. 1,

[0023]FIG. 4 is a detail view of FIG. 3,

[0024]FIG. 5 is an alternative form of embodiment of FIG. 3, and

[0025]FIG. 6 is a sectional view of FIG. 5.

[0026]FIG. 1 depicts a laminated ball joint 10, for example foranti-roll bar (not depicted) of a high speed train. This ball joint 10comprises a straight support 20 extending along a main axis ofelongation xx′ and an elastically deformable member 30 intended inparticular to react the axial and radial forces while at the same timeallowing significant rotational deflection.

[0027] The elastically deformable member 30 comprises at least onelaminated structure 35 surrounded by a preloading means 40. A detaileddescription of this elastically deformable member 30 is given later on,in conjunction with FIGS. 3 and 4 in particular.

[0028] As can be seen in FIG. 2, the preloading means 40 and thelaminated structure 35 are concentric, the laminated structure 35 beingformed, as will be seen later on, of a (approximately radial) stack oflayers 32 and 34 made of materials with different hardnesses.

[0029]FIGS. 3 and 4 show in greater detail the layers 32 and 34 of eachlaminated structure 35. As can be seen in particular in FIG. 3, theelastically deformable member 30 in fact comprises two laminatedstructures 35 which are annular and coaxial and which meet at a joiningplane perpendicular to the axis xx′ of the support 20. They need to bemounted on the support in such a way that their respective geometriccenters are roughly coincident. In practice, this center is locatedapproximately at the intersection of the axis xx′ and of the joiningplane of the two laminated structures 35, which, when the ball joint ispivoted (conical stressing) allows the layers to work in a shear.

[0030] The laminated structures are surrounded by sleeve tubes 42 and 44respectively, for example made of steel and acting, once fixed to oneanother, as a means for preloading (particularly for axially preloading)the laminated structures 35.

[0031] Each laminated structure 35 thus consists of an alternating stackof layers 32 of an elastically deformable flexible material such asnatural rubber and of layers, or cups, 34, made of a more rigidmaterial, such as metal (building steel in particular).

[0032] An elastically deformable flexible material is to be understoodas meaning a material deemed to be hyperelastic, that is to say onewhich has the ability to be deformed elastically in at least one mostencouraged direction to a large extent, by contrast with a rigidmaterial which has a small zone of elastic deformation.

[0033] In addition, each laminated structure 35 begins and ends thestack with a layer 32 a/32 b of flexible material. Thus, one layer 32 ais in contact with one of the sleeve tubes 42 or 44, the other layer 32b is in contact with a core 50 of spherical shape belonging to theelastically deformable member 30 and possibly also secured to thesupport 20. Adhesion between the rubber layers 32 and the metal parts(core 50, preloading means 40, cups 34) is achieved when the part ismolded by injecting rubber between the cups, through a chemicalreaction. This embodiment gives far better performance than bonding orany other means of connection.

[0034] Of course, each laminated structure 35 has an approximatelyhemispherical interior and exterior shape, which means that it perfectlyfollows the external shape of the spherical core 50 and the internalshape of the sleeve tubes 42 and 44.

[0035] As can be seen in detail in FIG. 4, the thickness of each layeris relatively small, for example of the order of 1 mm in this instance.The dimensions depend on the use to which this ball joint is to be put,and are therefore given only by way of indication. It is, however,important that the metal cups 34 have sufficient strength at the time ofmolding that they do not deform under the pressure of the rubber.Likewise, if the layers 32 of rubber are too thin, the material willhave difficulty in flowing uniformly between the cups 34 duringinjection, and there will then be a risk of creating empty pockets inthe stack.

[0036] This ball joint 10 is particularly simple to produce and toassemble.

[0037] First of all, a first Laminated structure 35 is produced,trapping, during a first phase of injection-molding under pressure,rubber between the various cups 34 and between a first cup 34 a and ahalf core 52, and between a last cup 34 b a sleeve tube 42. A unitassembly approximately in the shape of a ring or half ball joint is thuscreated. As the metal cups 34 have a hemispherical shape, as does theinternal surface of the sleeve tube 42 and the external surface of thehalf core 52, the layers 32/32 a/34 a of rubber also have ahemispherical shape.

[0038] The molding operation is repeated to form a second unit assembly(half ball joint) that complements the first, with a second sleeve tube44, a second laminated structure 35 and a second core 54.

[0039] These two half ball joints are then mounted around the support 20so as to form the ball joint 10.

[0040] To do that, the two half cores 52 and 54 and the sleeve tubes 42and 44 and the laminated structures 35 are Drought axially closertogether so that the half cores touch to adopt a spherical shape. Atthat moment, the two sleeve tubes 42 and 44 are not yet in contact. Theinside diameter of the core and the outside diameter of the support arechosen in such a way as to avoid any axial or torsional slipping of onehalf core with respect to the other when the ball joint is in use.

[0041] The sleeve tubes 42 and 44 are then forcibly brought closertogether so that they too come into contact with one another at contactsurfaces 42 a and 44 a which extend along a plane of sectionperpendicular to the axis xx′ of the support 20. It is contrived that,when the half cores 52 and 54 are butted against each other, the sleevetubes cannot come into contact with one another unless a certain axialforce is exerted. In other words, there is a certain axial clearancebetween the two sleeve tubes before they are fixed together.

[0042] Next, the sleeve tubes 42 and 44 are held one against the otherand are connected, for example by a welding technique (preferably laserspot welding) or by any other appropriate means which in particular isable to react the axial forces generated by the preloading.

[0043] While the weld 48 is being formed, care is taken to prevent therubber layers 32 b from being damaged by the heat released. This is madeeasier in particular by spot welding and by a suitable design of therubber layers avoiding situating them too close to the welding zone.

[0044] Once the circumference of the sleeve tubes has been welded, it ispossible to anticipate carrying out an additional machining operation onthe part in order to remove any excess weld material.

[0045] It will be noted that both the sleeve tubes 42/44 and the rings32/3 are identical and arranged symmetrically on each side of a planeperpendicular to the axis xx′, so as to form a ball joint 10 which iswell balanced (give or take the manufacturing tolerances) about thisplane of section.

[0046] Bringing the sleeve tubes closer together along the axis xx′ ofthe support, and fixing the sleeve tubes together by welding so as tofill the clearance left between them, have the effect of creating axialpreload in the laminated structures by shear and compression of therubber layers 32. This preload is particularly useful and in particularmakes it possible to limit the work that the rubber does in tension,which allows for a longer life.

[0047] All that then remains is for the ball joint 10 thus produced tobe fixed to an anti-roll bar (or to a damping arm) or to a connectinglink for a bogie or body of a high speed train.

[0048] In general, this type of laminated ball joint has an elasticreturn force or moment in all directions, that is to say that applying aforce in one direction causes a more or less proportional displacementin that direction and that applying a conical torsion angle (about anyaxis perpendicular to the axis xx′) causes the appearance of a moment,this also being more or less proportional.

[0049] There is also a total absence of slippage of the elements oneagainst the other, unlike in current ball joints, because the rubberlayers in fact experience shear in all possible directions of rotation.

[0050] The production of this laminated ball joint makes it possible toget as close as possible to the model of the theoretical ball joint(three degrees of freedom in rotation, no degrees of freedom intranslation) by virtue of higher stiffnesses in translation (axial andradial) and lower stiffnesses in rotation (torsional and conicaltorsional) than with conventional (unlaminated) rubber-metal ball jointsand thus make it possible, for the same volume, to have higher forcesand deflections than in the prior art.

[0051]FIGS. 5 and 6 depict an alternative form of embodiment in whichthe ball joint 10 comprises two laminated structures 135 each consistingof a stack of layers 32 of elastic material, such as natural rubber, andof layers 34 of a more rigid material, such as a metal (conventionalsteel). These laminated structures 135 in the form of half shells with ajoining plane passing through the axis xx′ of the support 20, aresurrounded by half sleeve tubes 142 and 144 with the same plane ofsection, these half sleeve tubes acting as means 40 for preloading thelaminated structures 135.

[0052] Thus, in contrast with the previous embodiment, the half shellsand the half sleeve tubes are therefore not annular and no longer meeton a plane perpendicular to the axis xx′ but on a plane passing throughthis axis xx′, as can be seen in FIG. 6. The half shells (and the twohalf sleeve tubes) therefore extend along the axis xx′, each matchinghalf the spherical shape of the core 50 support 20 over which thelaminated structure is molded.

[0053] The way in which this elastically deformable member 30 isproduced is similar to that of the previous embodiment, except that thecomplete ball joint is made in a single shot by molding the rubberbetween the cups 34, the half sleeve tubes 142 and 144 and the core 50.Preloading (mainly radial) is exerted at the time of this molding by thehalf sleeve tubes 142 and 144 on the laminated structures.

[0054] An external tube 160 may also be crimped around the sleeve tubesto hold the assembly in place and provide the preload, although this isnot necessary, it being possible for this preload to be provided byassembly.

[0055] The properties obtained with this type of ball joint areapproximately equivalent to those of the first embodiment, except thatthe first ball joint has the same radial and conical stiffnessregardless of the direction in which the radial force or conical momentis applied.

[0056] It must of course however be understood that these examples aregiven purely by way of illustration of the subject of the invention,which they do not in any way restrict.

[0057] Thus, this type of ball joint may find a use outside the field ofanti-roll bars, for example in the field of attachments for dampers,draught arms, braking mechanisms, couplings, controls for pneumaticdevices or guide mechanisms. Nor is the ball joint according to theinvention restricted to use in the rail field; it may be applied to theaeronautical or automobile industry.

[0058] Furthermore, the spherical shape of the core 50 may be machineddirectly on the support, without having to resort to an intermediatecomponent.

[0059] Of course the number and thickness of the layers can varyaccording to the required characteristics (radial, torsional and conicaltorsional stiffness) and levels of deflection and load desired for thesethree types of stressing. The result, in terms of layer thicknessesmainly, is a compromise between the radial stiffness, on the one hand,and the torsional and conical stiffness, on the other, and the forcesand angles to which the ball joint is subjected (maximum values andfatigue value).

[0060] The flexible layers may be made of natural rubber or of any othermaterial with hyperelasticity properties.

[0061] Finally, the welding of the sleeve tubes may be replaced by afixing using several screws which is arranged on lugs of each sleevetube, by crimping, or by any other equivalent means.

1. Connecting ball joint (10), for example an anti-controll bar of arunning vehicle, said ball joint (10) comprising a straight support (20)running along a general axis of elongation (xx′) and an elasticallydeformable member (30) mounted around this support (20), characterizedin that the elastically deformable member (30) comprises at least onelaminated structure (35; 135) made up of (a) layer(s) (32; 32 a; 32 b)of elastically deformable flexible material and of (a) layer(s) (34; 34a; 34 b) of more rigid material.
 2. Ball joint (10) according to claim1, characterized in that the elastically deformable member (30)comprises means (40) for preloading its laminated structure (35; 135).3. Ball joint (10) according to claim 2, characterized in that theelastically deformable member (30) comprises two coaxial annularlaminated structures (35) and two annular sleeve tubes (42, 44) eachmounted around one laminated structure (35) to preload their elasticallydeformable flexible layers (32; 32 a; 32 b) once these sleeve tubes (42,44) have been connected together using fixing means, the ball joint (10)having a plane of section roughly perpendicular to the axis xx′ of thesupport.
 4. Ball joint (10) according to claim 3, characterized in thatthe two sleeve tubes (42, 44) each have a contact surface (42 a, 44 a)perpendicular to the axis (xx′) of the support (20, and are weldedperipherally at these surfaces.
 5. Ball joint (10) according to claim 2,characterized in that the elastically deformable member (30) has a planeof section passing through the axis xx′ of the support and comprises twoapproximately hemispherical laminated structures (135) extending alongthe axis xx′ and two half sleeve tubes (142, 144), also approximatelyhemispherical, each surrounding a laminated structure (135) to preloadtheir elastically deformable layers (32; 32 a; 32 b).
 6. Ball joint (10)according to claim 5, characterized in that an outer tube (160) iscrimped around the half sleeve tubes (142, 144).
 7. Ball joint (10)according to any one of the preceding claims, characterized in that eachlaminated structure (35; 135) consists of an alternation ofapproximately hemispherical layers (32; 32 a, 32 b) of hyperelasticflexible material and of approximately hemispherical layers (34; 34 a;34 b) of a more rigid material.
 8. Ball joint (10) according to claim 7,characterized in that each laminated structure (35) has a hyperelasticflexible layer (32 a) at each of its ends, one in contact with aspherical core (50), and the other in contact with the reloading means(40).
 9. Ball joint (10) according to any one of the preceding claims,characterized in that the hyperelastic flexible material is a naturalrubber and the rigid material is a metal.
 10. Bail joint (10) accordingto any one of the preceding claims, characterized in that the layers(32; 32 a; 32 b) of elastically deformable flexible material and thelayers (34; 34 a; 34 b) of rigid material each have a thickness of theorder of 1 mm.
 11. Ball joint (10) according to any one of the precedingclaims, characterized in that it has a radial stiffness which is high bycomparison with its torsional and/or torsional conical stiffness. 12.Ball joint (10) according to any one of the preceding claims,characterized in that the elastically deformable flexible layers (32)are connected to the more rigid layers (34) in such a way that theseflexible layers (32) experience, in operation, mainly shear forces, withno slipping with respect to the more rigid layers (34).
 13. Anti-rollbar for a running vehicle, for example for a high speed train,characterized in that it is equipped with a ball joint (10) according toany one of the preceding claims.